As a service to the community this article is available to view for free. Use your via AAAS ID to log in or register for a free account

Via your Institution

Log in through your institution

If your organization uses OpenAthens, you can log in using your OpenAthens username and password. To check if your institution is supported, please see this list. Contact your library for more details.

Log in through your institution

You may be able to gain access using your login credentials for your institution. Contact your library if you do not have a username and password.

Free with registration

Science research is available free with registration one year after initial publication. To get your free access please visit our registration form.

Abstract

Carbon dioxide is a primary component of the martian atmosphere and reacts readily with water and silicate rocks. Thus, the stable isotopic composition of CO2 can reveal much about the history of volatiles on the planet. The Mars Phoenix spacecraft measurements of carbon isotopes [referenced to the Vienna Pee Dee belemnite (VPDB)] [δ13CVPDB = –2.5 ± 4.3 per mil (‰)] and oxygen isotopes [referenced to the Vienna standard mean ocean water (VSMOW)] (δ18OVSMOW = 31.0 ± 5.7‰), reported here, indicate that CO2 is heavily influenced by modern volcanic degassing and equilibration with liquid water. When combined with data from the martian meteorites, a general model can be constructed that constrains the history of water, volcanism, atmospheric evolution, and weathering on Mars. This suggests that low-temperature water-rock interaction has been dominant throughout martian history, carbonate formation is active and ongoing, and recent volcanic degassing has played a substantial role in the composition of the modern atmosphere.